If you thought the creation of the "Do Not Call Registry" had solved the problem of telemarketers bombarding people with unwanted calls, think again.

Complaints about telemarketers have continued to climb since the Federal Trade Commission established the registry 2003. They now stand at an all time high -- almost 4 million in 2012 -- according to the FTC.

What can you do to fight back? Plenty, say experts: You can use new technology that detects and deflects telemarketing calls automatically. You can deliberately drive telemarketers nuts. Or you can do both.

Intrusive calls fall into two categories. The first are calls from legitimate telemarketers, in which the pitch comes straight from a real live person. Louis Greisman of the FTC's Bureau of Consumer Protection testified before Congress in 2013 that the Do Not Call Registry has been "tremendously successful" in protecting the 221 million people who have registered.

Changes in telemarketing technology, however, have introduced calls that fall into a second category. These fully automated solicitations -- so-called robocalls -- are sent out by the million by computers. A pre-recorded solicitation asks the consumer to respond by, say, pressing "1" on his or her keypad. Only after that does a human pitchman comes on the line. Robocalls, according to the FTC, are illegal -- unless the consumer has first given his or her express permission, in writing, to receive them.

Many robocalls peddle fraudulent goods and services that cause significant economic harm, Greisman said. In his 2013 testimony, he told Congress the FTC was using every tool at its disposal to fight them. For example, the Commission announced a challenge offering $50,000 in prizes to private-sector innovators who could come up with ways to block such calls.

Last April, software developer Aaron Foss won $25,000 from the FTC for a blocking system he calls Nomorobo. Up and running since October, the service is now used, Foss said, by some 45,000 consumers who subscribe to it for free. By Foss' estimate, Nomorobo currently is blocking 1.3. million automated callers.

Many such callers don't care about the Do Not Call list, Foss told ABC News either because they're overseas, and thus beyond the FTC's reach, or because it's easy for them, when shut down by authorities, to spring back into action in a new venue. They're more like email spammers than traditional telemarketers, he said.

Nomorobo piggybacks off a feature offered by most major phone carriers called "simultaneous ring." Foss said it's similar to call-forwarding.

When a consumer signs up with Nomorobo, he gets assigned a new phone number that rings simultaneously when somebody calls his existing landline or cell phone. When a robocall comes in, it rings once on the consumer's existing number and again, simultaneously, on the Nomorobo number, where an algorithm determines in a fraction of a second whether it's from a real person or from a robo-caller. If from the latter, a recording asks the caller to enter a number on their keypad.

Since no human being is yet on the line, no response is made, and Nomorobo dismisses the call before it can ring again. Thus, the consumer knows that any call that rings more than once is legit -- or at least that it comes from a real person rather than a robot.